Clutch and pawl control for carriage returen mechanisms



Feb. 3, 1959 B. w. WITTWER CLUTCH AND PAWL CONTROL FOR CARRIAGE RETURN MECHANISMS Filed Nov. 19, 1954 2 Sheets-Sheet 1 INVENTOR. \igyl. WITTWER BERN u, [MMM ATTORNEY Feb. 3, 1959 B. w. WITTWER 2,872,013

CLUTCH AND PAWL CONTROL FOR CARRIAGE RETURN MECIXANISMS Filed NOV. 19, 1954 v 2 Sheets-Sheet 2 JIIIIIIIIIIIIIII" 3 2 2 INVENTOR. 2 BERNA w. WITTWER I 3 W 2 (U Kim m m:

ATTORNEY United States Patent 7 cLUrcn AND PAWL CONTROL FOR CARRIAGE. RETURN MEcHANrs s Application November 19, 1954, Serial No. 469,915

4 Claims. ('Cl. 197-66) Y., assignor This invention relates to typewriters and more particularly to an improved escapement pawl control mechanism. During a carriage return movement in the standard IBM electric typewriter, a clutch is energized which exerts a pull on a tension tape to pull the carriage until the left hand margin is positioned for printing. During this movement, the escapement pawls are lifted out of the escapement rack and then dropped back into place just before the carriage reaches the left hand margin position.

With such a mechanism, and particularly during a repeat line spacing operation (which is a result of carriage return operation), the pawls are lifted out of the escapement rack and restored to it for each line space operation, and on occasion, the pawls may not get back into the proper rack tooth whereupon there will be a misalignment of the left hand margin.

Accordingly, it is a first object of this invention to provide an improved pawl control mechanism wherein the escapement pawl remains in the rack during a repeat line spacing operation.

In the improved IBM electric typewriter, an air cushion has been installed to reduce the shock of the carriage return movement. Because of the addition of this air cushion, it s necessary to pull the carriage all theway into the left hand margin position, rather than let it coast in as was done with the old machine.

Further, it is necessary to hold the escapement pawl out of engagement with the escapement rack while the carriage is being returned since the drag of the pawls might interfere with the carriage being restored completely to the left hand margin position.

Therefore, it is a further object of this invention to provide a new pawl control mechanism operable on the carriage return movement to lift.the pawls out of the escapement rack until the carriage is almost in its left hand margin position whereupon the pawls are dropped back into the escapement rack.-

It is a further object of this invention to provide an improved pawl control mechanism which is operable to maintain the pawls in the escapement rack so long as the carriage is within a predetermined distance from theleft hand margin position. j

It is a still further object of this invention to provide an improved clutch control for driving the carriage retum mechanism which clutch control will be held latched in driving position until the carriage is wanna few thousandths of an inch of the left hand margin position, and then unlatched'.

Other objects of the invention will be pointed outvin the following description and claims and illustrated in the accompanying drawings, which disclose,.by way of example, the principle of the invention and the best mode, which has been contemplated, of applying that principle. I

In the drawings: l

v Fig. 1 is a rear elevation of portions of the carriage and pawl control mechanism of an IBM typewriter. w

2,872,013 Patented Feb. 3, 1959 pawl con-- Briefly, this invention relates to a mechanism which isoperable in response to a carriage return operation to lift.

the escapement pawl out of the escapement rack and hold it latched out until the carriage is within one-third of an inch of the left hand margin position, whereupon the latching mechanism will be unlatched to drop the pawls into the escapement rack where they will remain irrespective of repeat line spacing operations until the carriage has moved about one-third of an inch from the left hand margin position.

Further, the mechanism includes a device for -unlatch-- ing the carriage return clutch when the carriage is approximately at the left hand margin position.

With reference to the drawings and more particularly to Fig. 2, the carriage return key lever 2 is shown p'ositioned for operation of the carriage return cam 4 in a well known manner. Briefly, the depression of the carriage return key lever brings the cam 4'into engagement with a power roll 6, causing the cam to make one com plete rotation, or flip cycle, which, in turn, pivots the cam bracket 8 counterclockwise about its pivot point 10 to exert a pull on link 12.

The pull on link 12 pivots a bell crank 14 about its supporting stud 16 which is carried by arm 17 supported by the typewriter frame. The counterclockwise pivoting of the bell crank 14 exerts an inward pull on the stud 20 which pulls the pivoted clutch control arm 22 counter-. clockwise'about itssupporting pivot 23 thereby'exerting frictional force between the faces of two clutch discs 24 and 26, which action drives the tape reel 28 clockwise under the influence of the continuously rotating power roll 6. This action, as more particularly explained in U. S. Patent No. 1,955,614 causes the tape, reel 28 to wind up and exert a pull on tape 30 which is directed around pulley 32 thereby exerting a pull in the direction of the arrow 34 to drive the carriage of the typewriter towards theleft hand margin position.

As the clutch bell crank 14 is rotated counterclockwise I about its supporting stud 16, a clutch latch 36 is pivoted counterclockwise about'its'pivot 38 in response to the action of spring 40 until latch 36 is brought into engagement with a shoulder 42 on the bell crank 14 thereby latching the bell crank in the operative or clutch engaging position. j

Simultaneously with the counterclockwise pivoting of the clutch bell crank 14, a force is exerted on a link 44 to rock bell crank 46 clockwise about its supporting pivot 48 thereby exerting a pull in the direction ofthe arrow 50 on .the link 52. An intermediate pawl release lever 54 is pivoted about screw 56, secured to' the typewriter frame, whereby the pull on link '52 rocks the intermediate pawl release lever 54 counterclockwise from its Fig. 2 position, thereby causing an integral ear 58 to be raised for a purpose here inafter explained. a A pawl release trigger 64 is shown in Fig. 1 as comprising a pair of arms 66, 68 which are pivotally connected at their juncture by screw or pin 70. The arm 66 is provided with an car 72, which is connected by spring 74 to a portion of the typewriter frame. The arm 68 is pivotedabout screw or stud 56 so that an upward thrust of the. ear 58 of the intermediate pawl release lever, when it engages a lip 76 carried by the arm 66, will exert a force 3 normally along the top of the'screw 60, thereby limiting the counterclockwise movement ofthe arm 68 and hence the pawl release trigger 64. The extension 78 is engageable with an car 82 carried by a pawl release lever 84 (see Fig. 4). Y

In Fig. 4, the pawl release lever 84 is shown pivotable on the typewriter frame about a screw or other supporting stud 86. The pawl release lever has a downwardly extending arm 88 and inwardly extending arm 90 and an upwardly extending arm 92 which is positioned for engagement with the escapement pawl 94 and to pivot the latter about its supporting stud 96.

With this mechanism, the clockwise pivoting of the pawl release trigger 64 (Fig. l) causes the extension 78 to engage the car 82 thereby pivoting the pawl release lever 84 about its supporting stud 86 lifting the downwardly extending arm 88 away from an escapement rack 98 and causing the upwardly extending arm 92 to engage the pawl 94 to pivot the same about its supporting stud 96 and thereby lift the pawl out of engagement with the escapement rack.

The pawl will stay out of the escapement rack so long as the trigger 64 stays engaged with the ear 58 of the intermediate pawl release lever 54. However, when the lip 76 is disengaged from the car 58, then, the trigger 64 is free to pivot counterclockwise about its supporting stud 56 thereby disengaging the extension 78 from the ear 82 of the pawl release lever 84 so that the latter will fall back into its normal position (shown in Fig. '4) and thereby cause the escapement pawl to engage the escapement rack.

In order to bring about the unlatching of the pawl release trigger 64 at a suitable time, so as to get the pawls back into engagement with the escapement rack just before the carriage reaches the left hand margin position, the adjustable margin stop 100 (Fig. 3) which is carried by the moveable typewriter carriage is provided with a shoulder 102 for engaging a complementary hook 104 on a margin control lever 106. The latter is slidably supported along the typewriter frame by means of studs or set screws 108, 110 which passed through elongated aperture 112, thereby permitting the margin control lever to slide axially.

As shown in Fig. 3, the shoulder 102 has engaged the corresponding hook 104 and accordingly, the margin control lever 106 has been moved to the left in Fig. 3. The margin control lever has an car 114, (Fig. 1) engageable with a margin control bell crank 116, which in turn, is pivoted about a supporting stud 118. The margin control bell crank has a'nose 120 which is engageable with the car 72 carried by the arm 66 of the trigger 64. Accordingly, as the margin control bell crank is pivoted counterclockwise as viewed in Fig. 1, the nose 120 engages the ear 72 which then pivots the arm'66 counterclockwise about stud 70 until the shoulder 76 is released from the path of the ear S8, whereupon the trigger 64 is pivoted counterclockwise about its supporting stud 56 so that the extension 78 is moved out of engagement with the ear 82 thereby permitting the pawl release lever 84 to pivot clockwise as viewed in Fig. 4 about its supporting stud 86 back into its rest position.

As the carriage moves towards its left hand margin position (to the left as viewed in Fig. 1) inter-engagement of the margin stop 100 and margin control lever 106 will pivot the margin control bell crank 116 counterclockwise about its supporting stud 118 to trip the trigger 64 and thereby permit the pawls to be dropped back into engagement with the escapement rack. Further, as long as the carriage stays adjacent the left hand margin position, the nose 120 prevents the shoulder 76 from engaging the car 58, and accordingly, the pawls can never be lifted out of the escapement rack. When the carriage moves about three letter spaces away from the left hand margin position, however, then the nose 120is removed from the path of the ear 72 so that the trigger 64 can latch into engagement with the lever 54 tolift the, pawls. out

. of the escapement rack, upon the operation of the carriage return mechanism.

Clutch unlatching mechanism Referring again to Fig. 2 of the drawings, it was pointed out that latch 36 is moved into engagement with the shoulder 42 of the bell crank 14 to hold clutch control arm 22 in operative engagement. If the latch 36 is pivoted clockwise aboutits supporting stud 38 out of engagement with the shoulder 42, a spring 43 which interconnects the bell crank 14 and a frame car 45, will pivot the bell crank 14 clockwise about its supporting stud 16, thereby disengaging the clutch control arm 22. The latch 36 may be pivoted clockwise to unlatch the bell crank 14 by exerting a pull on a link 122. Link 122, in turn, is connected to a bell crank 124 which is pivotally supported along with bell crank 46 about the stud 48, and has a crank arm 126 which is connected by means of a link 128 to an unlatching lever 130. The, latter is pivotally supported bymeans of a screw or stud 132 on the typewriter frame, and carries an operating arm 134 including a bent over portion 136 which is positioned for engagement with the margin control bell crank 116 (see Fig. 3).

. Specifically, as the margin control bell crank is pivoted counterclockwise about its supporting stud 118, the bell crank will engage the bent over portion 136, thereby pivoting the unlatching lever 130 counterclockwise about its supporting stud 132 to exert a pull on link 128 (to the right in Fig. 3 and left in Fig. 2).

Referring again to Fig. 2, the pullon link 128 will pivot the bell crank 124 counterclockwise about its supporting stud 48, thereby exerting a pull on the link 122 to pull the latch 36 out of engagement with the shoulder 42, permitting spring 43 to rotate the clutch bell crank 14 clockwise to restore it to its original position and disengage the clutch control arm 22.

Air cylinder With reference now to Fig. 1 of the drawings, an air cylinder 142 is shown comprising a cylinder portion 144, and a piston 146 which is connected by means of a rod 148 to an air cylinder bell crank 150 in turn pivotally supported at 152 on the typewriter frame. The air cylinder bell crank 150 has an operating arm 154 engageable with an arm 156 integral with the margin control belt crank 116. With this structure, as the carriage is moved toward the left hand margin position (to the left in Fig. 1), the margin stop engages the margin control lever 106 to pivot the margin control bell crank 116 counterclockwise about its supporting stud 118, thereby causing the margin control bell crank arm 156 to act on the operating arm 154. Operating arm 154 is pivoted about its supporting stud 152 to drive the shaft 148 and hence piston 146 to the left to absorb the shock of the carriage.

Operation In operation, the depression of the carriage return lever causes the cam 4 to fiip over as driven by the power roll 6 thereby exerting a pull on the bell crank 46 to rotate the intermediate pawl release lever 54 thereby lifting the escapement pawl out of the rack. The carriage is then driven toward the left hand margin position by tape 30 until the margin stop engages the hook 104 of the margin control lever 106. The margin'control lever will rotate the margin control bell crank 116 counterclockwise about the supporting stud 118 until it trips the trigger 64 to drop the pawls back into engagement with the escapementrack. Simultaneously, the counterclockwise pivoting of the margin control bell crank 116 operates the air cylinder 142 to absorb the shock of the carriage. Just as the margin control bell crank 116 reaches the extent of its counterclockwise rotation, it acts on the bent over portion 136 of the clutch release lever to pivot the latter about its supporting stud 132 thereby knocking out the clutch as the carriage reaches its left hand mar- 76 gin position. The escapement pawl remains in the escapement rack so long as the carriage is adjacent the left hand margin position, irrespective of the number of times the carriage return lever i operated thereby assuring alignment of the left hand margin during repeat line spacing.

While there have been shown and described and pointed out the fundamental novel features of the invention, as applied to a preferred embodiment, it will be understood that various omissions and substitutions and changes in the form and details of the device illus trated and in its operation may be made by those skilled in the art, without departing from the spirit of the invention. It is the intention, therefore, to be limited only as indicated by the scope of the following claims.

What is claimed is:

1. In a typewriter having a carriage, a power driven carriage return mechanism and an escapement mechanism comprising an escapement rack and a pawl selectively engageable with said escapement rack to effect a carriage escapement operation, a device for releasing the pawl from the escapement rack and holding it released during a carriage return operation until the carriage reaches a predetermined distance from its left hand margin position, said device comprising a pawl release lever pivotally mounted on the typewriter frame for movement from a rest position to a pawl releasing position, a pawl release bell crank pivotally mounted on the typewriter frame adjacent said pawl release lever, a trigger interconnecting said pawl release bell crank and said pawl release lever, a latch in said trigger providing a releasable interconnection between said pawl release bell crank and said pawl release lever whereby when said latch is in operative position, the rocking of said pawl release bell crank will move said pawl release lever to its pawl releasing position, means responsive to a carriage return operation for pivoting said pawl release bell crank to release said escapement pawl from said escapement rack, and means responsive to the carriage position for tripping said trigger latch to disconnect said pawl release lever and permit said escapement pawl to drop back into the escapement rack irrespective of the position of said pawl release bell crank.

2. In a typewriter having a carriage, a power driven carriage return mechanism and an escapement mechanism comprising an escapement rack and a pawl selectively engageable with said escapement rack to effect a carriage escapement operation, a device for releasing the pawl from the escapement rack and holding it released during a carriage return operation until the carriage reaches a predetermined distance from the left hand margin position, said device comprising a pawl release lever pivotally mounted on the typewriter frame, a pawl release bell crank pivotally mounted on the typewriter frame adjacent said pawl release lever, a trigger interconnecting said pawl release bell crank and said pawl release lever, a latch in said trigger providing a releasable interconnection between said pawl release bell crank and said pawl release lever whereby when said latch is in operative position, the rocking of said pawl release bell crank will lift the pawl out of said escapement rack, means responsive to a carriage return operation for pivoting the said pawl release bell crank to lift the pawl out of said escapement rack, and means responsive to the carriage position for tripping said trigger latch to release said pawl release lever irrespective of the position of said pawl release bell crank, said carriage position responsive means comprising a margin stop mounted on said carriage, a margin lever mounted on said typewriter frame for engagement with said margin stop as said carriage traverses a predetermined distance adjacent its left hand margin position, a margin lever bell crank pivotally supported on said typewriter frame for rocking movement in response to the operation of said margin lever, said margin lever bell crank having an integral portion 6 engageable with said trigger to release said trigger latch while the carriage is traversing a predetermined distance adjacent its left hand margin position.

3. In a typewriter having a carriage, a clutch operated carriage return mechanism including clutch latching means, a margin lever bell crank mounted for pivotal movement in response to the carriage approaching its left hand margin position, and an escapement mechanism comprising an escapement rack and a pawl selectively engageable with said escapement rack to effect a carriage escapement operation, a mechanism comprising a first device for releasing said pawl from the escapement rack and holding it released until the carriage reaches a predetermined dis tance from its left hand margin position and for holding said escapement pawl in said rack while said carriage iswithin said predetermined distance from its left hand margin position and a second device for unlatching said carriage return clutch when said carriage reaches its left hand margin position, said first device comprising a pawl release lever pivotally mounted on the typewriter frame for movement from a rest position to a pawl releasing position, a pawl release bell crank pivotally mounted on said typewriter frame adjacent said pawl release lever for movement from a rest position to an actuated position, a trigger interconnecting said pawl release bell crank and said pawl release lever, a releasable latch in said trigger whereby when said latch is in its operative position the rocking of said pawl release bell crank will lift said escapement pawl out of the escapement rack, a first clutch bell crank positioned for rocking movement to an operative position in response to the operation of said carriage return clutch, means interconnecting said first clutch bell crank and said pawl release bell crank for rocking the latter to its operative posititon in response to the operation of the carriage return clutch, and means responsive to the carriage position for releasing said trigger latch to drop the escapement pawl back into the escapement rack irrespective of the position of said pawl release bell crank, said second device comprising a clutch release arm pivotally mounted on said typewriter frame for rocking movement from a rest position to an operative position in response to the pivoting of the margin lever bell crank, and linkage means interconnecting said clutch release arm with said clutch latching means to release the latter as said clutch release arm is moved to its operative position.

4. In a typewriter having a carriage, an escapement mechanism comprising an escapement rack and a pawl selectively engageable with said escapement rack to effect a carriage escapement operation, and a power driven carriage return mechanism, a device for releasing the pawl from the escapement rack and holding it released during a carriage return operation until the carriage reaches a predetermined distance from its left hand margin position comprising a pawl release lever, means pivotally mounting the same for movement from a rest position to a pawl release position, a pawl release bell crank, means for moving said pawl release bell crank from a rest position to an operative position in response to a carriage return operation, latch means interconnecting said pawl release bell crank with said pawl release lever for movement of the latter to its pawl release position in response to movement of said pawl release bell crank to its operative position, and means responsive to the position of said carriage for releasing said latch means to drop said pawl back in the rack irrespective of the position of said pawl release bell crank.

References Cited in the file of this patent UNITED STATES PATENTS 1,955,614 Thompson et a1. Apr. 17, 1934 2,315,992 Von Reppert s Apr. 6, 1943 2,567,937 Hart Sept. 18, 1951 

